Final answer:
The third major group of steels, in addition to carbon steels and low-alloy steels, is high-alloy steels, which have greater amounts of alloying elements and are used for their special properties such as greater strength and corrosion resistance.
Step-by-step explanation:
The three major steel groups are carbon steels, low-alloy steels, and high-alloy steels. The major classifications of steel are defined by the different amounts and types of alloying elements added to iron and carbon. High-alloy steels contain greater amounts of alloying elements than low-alloy steels, which lend them specific properties, such as increased corrosion resistance or greater strength at high temperatures. These added elements include chromium, manganese, nickel, molybdenum, and others. Each type of steel is tailored for various applications, including building construction where their attributes such as strength and corrosion resistance are essential.